High speed synchronous optical communication networks are typically referred to as SONET/SDH networks. Conventionally, SONET/SDH transceivers transmit and receive at the same data rate. Thus, two SONET/SDH transceivers communicating with each other over an optical fiber link need to be configurable to operate at the same data speed, which can vary. This variable data rate requires that a machine or technician be able to configure the speed the two transceivers can communicate with each other at.
Typically, these SONET/SDH transmission equipment contain an input/output (IO) card that is designed to operate at particular operating data rate frequency. This maximum operating data rate frequency is primarily established and limited by the semiconductor transceiver devices comprising the transmitter and receiver and being designed for a specific data rate frequency.
In one conventional solution, outlined in an article entitled “A 0.155-,0.622-, and 2.488-Gb/s Automatic Bit-Rate Selecting Clock and Data Recovery IC for Bit-Rate Transparent SDH Systems” authored by J. C. Scheytt, G. Hanke and U. Langmann published in the December 1999 issue of IEEE Journal of Solid-State Circuits, there is described a system that provides an automatic bit-rate transceiver. This article describes the use of two clocking rates, analog elements i.e. low pass filter, threshold voltage generator, and voltage comparitor, relying on the relative frequency of the data edges. This transceiver circuit, disadvantageously, takes milliseconds to switch between different received data bit rates.
There is desired an improved SONET/SDH transceiver that is able to detect and receive data automatically and quickly, to set itself to operate at the highest and correct data rate frequency. The desired improvement would hopefully only use one clocking frequency, that is all digital, and requires significantly less time to detect and adjust to a new data bit rate.